PESHAWAR, Pakistan -- The Sina Diagnostic Center and Trust does not appear to be a menacing enterprise. The clinical pathology laboratory's 15 staff members conduct ultrasounds, X-rays and CAT scans and run free hepatitis and HIV tests for poor people and refugees in this teeming northwestern city.

That did not stop about a dozen Pakistani government revenue officers and police from marching up to the lab's second-story office this month to demand that the owner, Noor Zaman Mehsud, shut it down. They ushered patients and staff members outside, pulled down the metal gates and wrapped white cloth around the padlocks. Within 15 minutes, they were gone.

"They just said, 'You are a member of the Mehsud tribe, and we are going to seal up this business,' " Mehsud recalled. "My crime is that I belong to the Mehsuds."

Beyond the frustration of closing a business he ran for nine years and the sting of losing an income averaging $1,400 a week, the most vexing part of Mehsud's situation is that he is on the wrong side of the law. The Pakistani government has declared war on Taliban commander Baitullah Mehsud and his network of several thousand fighters in the nearby tribal district of South Waziristan. And under regulations formulated a century ago by British colonial rulers, Pakistan's tribes are still bound by a legal concept known as "collective responsibility," under which any tribal member can be punished for the crimes of another.

The crackdown on the Mehsuds was spelled out in an order from the top political official in South Waziristan, Shahab Ali Shah, on June 14. Because the Mehsud tribesmen had not handed over Taliban fighters, Shah wrote, he was satisfied that they had acted "in an unfriendly and hostile manner toward the state" and that the tribe's "people and their activities are prejudicial to peace and public tranquillity."

Senior government officials have said repeatedly that their target is Baitullah Mehsud and his followers, not his entire tribe, but Shah's wording was broader. He ordered the "seizure, where they may be found, of all members of the Mehsud tribe and confiscation of movable/immovable property belonging to them in the North-West Frontier Province and the arrest and taking into custody of any person of the tribe wherever he is found."

That sweeping order has led to the closure of dozens, perhaps hundreds, of businesses in towns such as Dera Ismail Khan, Tank and Peshawar in North-West Frontier Province, according to lawyers, human rights officials and residents. One South Waziristan political official, who spoke on the condition of anonymity, said 25 Mehsuds have been arrested in Dera Ismail Khan and Tank.

"This is the law of the jungle, not for civilized people. They are treating people like animals," said Noor Zaman Mehsud, the 39-year-old lab owner, who denied he had any connection to the Taliban. "If I am a criminal, they should arrest me. But they are giving other people's punishments to me."

A few hundred thousand people in Pakistan belong to the Mehsud tribe, a Pashtun network divided into three major clans: the Manzai, the Bahlolzai and the Shaman Khel. Although they are scattered across the country, their home territory is South Waziristan, which borders Afghanistan and is a refuge for fighters operating in both countries. For a civilian, it is not a welcoming place, caught as it is between the repressive rule of the Taliban and the military's preparations for a ground invasion. From the skies, Pakistani fighter jets and U.S. unmanned aircraft regularly bombard Taliban targets.

The violence has pushed tens of thousands of Mehsuds out of South Waziristan. But there is little respite wherever they turn.

"They are asking the people who are besieged, the people who have left their homes, 'Why you are not tackling the terrorists?' " said Said Alam Mehsud, a doctor from the same sub-tribe as Baitullah Mehsud. "Just imagine, what a demand. It's like if America asked me: 'Why are you practicing as a pediatrician? Why have you not captured Osama bin Laden?' "

The move to arrest and seize property of "hostile or unfriendly" tribal people is allowed under Section 21 of the 1901 Frontier Crimes Regulations, a legal framework developed to help the British Raj control rebellious Pashtuns. The regulations, which tribal leaders have tried to repeal or amend for years, give vast powers to the top official in each tribal district, known as the political agent. Aimal Khan, a tribal areas specialist with Sungi, a Pakistani humanitarian organization, said political agents are popularly referred to as "kings without crowns."

In the past, the regulations have been used to block tribal movements, recover hostages and punish those who attack government installations. Latif Afridi, a lawyer and expert on tribal laws, compared Shah's order to economic sanctions against a hostile country. The current pursuit of Mehsuds is not particularly widespread, but it remains an affront to human rights, he said.

"This is an order which is a remnant of the colonial days. Mehsuds should be treated as Pakistanis, their fundamental human rights respected," Afridi said. "It is a very cruel law, but so long as it is a law, I would definitely concede that the political agent has this power."

Habibullah Khan, a senior government official for the Federally Administered Tribal Areas, of which South Waziristan is a part, said the collective punishment policy does not mean the government will make "blanket arrests" of Mehsud tribesmen, but rather allows authorities to capture criminals. Another senior FATA official said five close supporters and financiers of Baitullah Mehsud had been arrested.

"We will be very choosy in our activities against the tribesmen in South Waziristan agency, as we know all of them are not terrorists," Khan said.

In June, Abdul Karim Mehsud, a lawyer, filed a petition with the Peshawar High Court asking for Shah's order to be repealed on the grounds that it is discriminatory and that taking such action in North-West Frontier Province is outside the jurisdiction of the tribal area political agent.

The FATA's Khan argued that arrest warrants for Mehsud tribesmen from South Waziristan are applicable outside that region. Lawyers familiar with tribal regulations said the Supreme Court has been divided on the issue. Lawyer Mehsud said last week that his petition had been denied.

"The actions by the government against the Mehsud people are pushing them back toward the Taliban," said Saleh Shah Qureshi, a senator from South Waziristan. "People are going back to Waziristan."

Bilal Mehsud, 24, is not sure where to turn. His father's cement business, Madina Traders in Peshawar, was shuttered last week by a South Waziristan official and tribal police. He lives in Saudi Arabia but is home on vacation. Now police have issued arrest warrants for him and his father, he said, adding, "I'm not sure what crime we have committed."

Noor Khan Mehsud, who along with other tribesmen formed a volunteer committee to help displaced Mehsud families in Dera Ismail Khan, said local authorities have been slow to register the refugees.

"There is no government support," he said. "Officials have closed doors for us, and we are considered militants. Where should we go?"

Special correspondent Shaiq Hussain in Islamabad contributed to this report.